#include <stdio.h>

/* No recursion and no towers in memory: every move of the optimal
   solution can be read straight off the binary digits of its number. */
void hanoi_bits(int n) {
    const char *names = n % 2 == 1 ? "ABC" : "ACB";
    unsigned long long total = (1ULL << n) - 1;

    for (unsigned long long m = 1; m <= total; m++) {
        int disk = 1;
        for (unsigned long long bits = m; (bits & 1) == 0; bits >>= 1) {
            disk++;
        }
        int from = (int)((m & (m - 1)) % 3);
        int to = (int)(((m | (m - 1)) + 1) % 3);
        printf("Move disk %d from %c to %c\n", disk, names[from], names[to]);
    }
}

int main(void) {
    hanoi_bits(3);
    return 0;
}